Myocardial infarction (MI) is one of the most common diagnoses in hospitalized patients in industrialized countries. Myocardial Infarction generally occurs when there is an abrupt decrease in coronary blood flow following a thrombotic occlusion of a coronary artery previously narrowed by atherosclerosis. Infarction occurs when a coronary artery thrombus develops rapidly at a site a vascular injury, which is produced or facilitated by factors such as cigarette smoking, hypertension and lipid accumulation. In most cases, infarction occurs when an atherosclerotic plaque fissures, ruptures or ulcerates and when conditions favor thrombogenesis. In rare cases, infarction may be due to coronary artery occlusion caused by coronary emboli, congenital abnormalities, coronary spasm, and a wide variety of systemic, particularly inflammatory diseases.
Although classical risk factors such as smoking, hyperlipidemia, hypertension, and diabetes are associated with many cases of coronary heart disease (CHD) and MI, many patients do not have involvement of these risk factors. In fact, many patients who exhibit one or more of these risk factors do not develop MI. Family history has long been recognized as one of the major risk factors. Although some of the familial clustering of MI reflects the genetic contribution to the other conventional risk factors, a large number of studies have suggested that there are significant genetic susceptibility factors, beyond those of the known risk factors (Friedlander Y, et al., Br Heart J. 1985; 53:382-7, Shea S. et al., J. Am. Coll. Cardiol. 1984; 4:793-801, and Hopkins P. N., et al., Am. J. Cardiol. 1988; 62:703-7). Major genetic susceptibility factors have not yet been identified.